Editor is removing hard returns from my posts

I’ve come across a few posts like this in regards to Safari, but I’m using Firefox. I’m hoping someone can help me.

No matter how many hard returns appear in the editor in visual mode, the actual post is always smooshed together. I’ve tried the </br> and <p> </p> tricks- and they do work, but only if I publish directly from html mode.

If I realize I need to fix something in the post, I can’t use the visual editor to fix it or I’ll have to go back and add <p> </p> to every paragraph.

I suspect it might be the theme, as I have other WP blogs that don’t have this problem- but other info on the web points to tinyMCE. Please Help!